Energy Self-Reliant States has developed a Google Map-based assumption of when cities and states will reach solar grid parity. In other words, the map shows when non-renewable commodity prices will equal, or be greater than, the cost of solar-generated power. The website describes it best: “Solar grid parity describes the moment when electricity from solar power is less costly than electricity from the existing grid. It’s a tipping point, when democratization of the electricity system not only makes political and economic sense, but becomes more competitive than using utility-delivered electricity.”
This map makes several assumptions, but as a general baseline it provides an interesting assessment of where and when solar power can be the most useful in different areas.